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Alexandrite

Green in sunlight. Red in lamplight. Color-changing alexandrite is nature’s magic trick.

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Chrysoberyl Variety

Alexandrite is the color-change variety of the mineral chrysoberyl.

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Green by Day

Alexandrite is bluish green in daylight or fluorescent light.

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Red by Night

Alexandrite is purplish red in incandescent light or candlelight.

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Star-shaped Twin

This alexandrite specimen is made up of three interpenetrant crystals.

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Brazilian Gem

Brazil is one of the most important alexandrite sources.

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Re-entrant Angle

Notches marking the edge of each crystal are called re-entrant angles.

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Overview

About Alexandrite

About Alexandrite Gem
Often described by gem aficionados as “emerald by day, ruby by night,” alexandrite is the very rare color-change variety of the mineral chrysoberyl. Originally discovered in Russia’s Ural Mountains in the 1830s, it’s now found in Sri Lanka, East Africa, and Brazil, but fine material is exceptionally rare and valuable.

Alexandrite Description Alexandrite History and Lore

Birthstones & Anniversaries

Alexandrite is a birthstone for June, along with pearl and moonstone. Alexandrite is also the gem for the 55th wedding anniversary.

1830

The year alexandrite was discovered in Russia’s Ural Mountains.


Czar Alexander II

Gem’s namesake who emancipated Russia’s serfs and was assassinated in 1881.


580nm

This absorption band allows alexandrite to shift from red to green when viewed under different light sources.


Facts

  • Mineral: Chrysoberyl
  • Chemistry: BeAl2O4
  • Color: Bluish green in daylight, purplish red in incandescent light
  • Refractive Index: 1.746 to 1.755
  • Birefringence: 0.008 to 0.010
  • Specific Gravity: 3.73
  • Mohs Hardness: 8.5

Where It's Found

map

Treatments

There are a number of processes used to alter the color, apparent clarity, or improve the durability of gems.

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Synthetics

Some gemstones have synthetic counterparts that have essentially the same chemical, physical, and optical properties, but are grown by man in a laboratory.

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Imitations

Any gem can be imitated—sometimes by manmade materials or by natural materials chosen by man to impersonate a particular gem.

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gem love

Why We Love This Gemstone

1
Color Change

Making alexandrite change color from green to red is the world’s most fun use of a penlight.

2
Light Source

This gem provides dramatic proof of how much the light source affects color in gems.

3
Phenomena

Alexandrite can show both color change and a cat’s-eye: two phenomena in one gem.

Quality Factors

Color

quality factors

Fine alexandrite is green to bluish green in daylight and red to purplish red in incandescent light.

Clarity

quality factors

Good quality alexandrite has few inclusions. Rarely, needle-like inclusions create a cat’s-eye.

Cut

quality factors

Alexandrite is most often available in mixed cuts. Its rarity means it is often cut to save weight.

Carat Weight

quality factors

Most cut gems weigh less than one carat. Larger, higher-quality gems rise in price dramatically.

Alexandrite Quality Factors: The Comprehensive Guide

Research

Explore sources, gemological research, and the role of gems in history.

Gem Localities of the 2000s

James E. Shigley, Brendan M. Laurs, A. J. A. (Bram) Janse, Sheryl Elen, and Dona M. Dirlam , Sep 6, 2010 Read Article

Winter 2002 Gem News International

, Dec 1, 2002 Read Article

Russian Flux-Grown Synthetic Alexandrite

Karl Schmetzer, Adolf Peretti and Olaf Medenbach, and Heinz-Jürgen Bernhardt , Sep 1, 1996 Read Article

Chrysoberyl and Alexandrite from the Pegmatite Districts of Minas Gerais, Brazil

Keith Proctor , Mar 1, 1988 Read Article